This invention relates to a method of recovering magnesium chloride from brines containing the chloride.
Magnesium chloride is one of the main sources of magnesium, the latter being a metal which has ever increasing use since it has remarkable mechanical properties for a metal of such very light weight. Sea water or natural brines represent a nearly endless reserve of this chloride. But the recovery of magnesium chloride from such natural raw materials is a lengthy operation which necessitates cumbersome apparatus. Another source of magnesium chloride is constituted by mineral salts of oceanic origin, for example carnallite, which is a double salt of potassium and magnesium chlorides (KCl.MgCl.sub.2.6H.sub.2 O). It is most often present along with varying quantities of other salts, primarily sodium chloride. Traditionally, the treatment of carnallite or carnallitic ores was directed primarily towards the recovery of potassium chloride. In such treatments, the cold or hot decomposition processes produce a waste liquor which is low in potassium chloride but rich in magnesium chloride. Other more recent methods, directed more particularly to the recovery of magnesium chloride, are based on the proposition that carnallite is decomposed underground and that there can be brought to the surface a brine which has a composition close to that of the discarded mother liquor which would be obtained by processing carnallitic ore at the surface. However, such magnesium chloride recovery techniques are not fully satisfactory and a need remains for improved processes.